Notice how frame interval is 49.69 ms, it says limited by main thread, but main thread frame interval is 29.9 ms.
Do you by any chance have Vsync enabled and fps locked at 30 fps? If so, try disabling Vsync. There is a known bug in the Vsync fps lock and it has exactly that effect, see screenshots in the last post of this thread:.
Frame rate limiter odd behavior - Self-Service / Bugs & Issues - Microsoft Flight Simulator Forums